Abstract This article discusses the H-bridge formation amongst functional groups containing different H-bridge acceptors with OH donors. A series of circular grids is introduced as a visual aid for the organization and the comparison of the diversity of H-bridges present in organic molecules, emphasizing in the case where the H-bridge donor is an OH group (primarily alcohols and phenols). The H-bridges are classified as “unlikely”, “less significant” and “significant” based on experimental and/or theoretical evidence, and analyzed in terms of electronic, steric, thermodynamic, substitutional, or situational effects. Using these grids, students can predict and classify the likeliness of an H-bridge interaction between common organic molecules and understand their effects in more complex systems.

Resumen Este artículo discute la formación de puentes de hidrógeno entre grupos funcionales con diversos grupos aceptores y OH donadores. Se presenta una serie de mallas circulares como ayuda visual para la organización y comparación de la diversidad de puentes de hidrógeno en moléculas orgánicas, haciendo énfasis en la presencia de un grupo OH (de alcoholes o fenoles, primordialmente) como donador de puente de hidrógeno. Los puentes de hidrógeno son clasificados como “poco probable”, “poco significativo” y “significativo”, de acuerdo con la evidencia experimental o teórica; y analizados en términos de efectos electrónicos, estéricos, termodinámicos, situacionales o de los sustituyentes. Nuestro objetivo es que el estudiante sea capaz de predecir y clasificar la probabilidad de interacción por puente de hidrógeno entre compuestos orgánicos comunes y comprender su efecto en sistemas más complejos.

In Part II of a three-part series, we discuss two factors absent from textbooks of general chemistry that are important in a discussion of teaching orbitals. First, atomic orbitals are shown systematically to comprise algebraic formulae in coordinates of not one but four sets (spherical polar, paraboloidal, ellipsoidal, spheroconical coordinates). Each formula has its corresponding shape as a surface of constant amplitude; some visual examples are provided. Second, the argument that molecular structure is incompatible with quantum mechanics is presented. Despite the utility of orbitals as mathematical functions in various calculations, they are intrinsically complicated for the traditional purpose of qualitative explanation of molecular structure.

In Part III of this series, we undertake a critique of the nature of application of orbitals to describe or to explain the structure and the binding within molecules and materials. Teaching orbitals in introductory chemistry presents five dilemmas that cannot be easily resolved. We thus conclude, based on mathematical realties, that orbitals are not essential until advanced courses. Even in advanced courses, we question the traditional choice of presenting an inadequate set of orbitals. When one recognizes, in a context of general chemistry, the irrelevance of orbitals as algebraic formulae to the observable properties and reactions of chemical substances, one can readily proceed to teach appropriate content effectively without invoking orbitals or analogous entities, based on our actual experience in teaching general chemistry over the years.

In Part I of a three-part series, we present an objective survey of the technical literature discussing the inclusion of orbitals in high-school and post-secondary general chemistry. We start with the definition of orbitals. The presentation of orbitals in secondary (high) school is presented with arguments for and against. The content of orbitals in the curriculum of general chemistry is presented and summarized in terms of 1) electron configuration, 2) periodic table, 3) molecular structure and 4) reactivity. Previous discussion in favor of and against each theme is presented. Recent research in chemical education is also reviewed.

Abstract The effect of substituents on the acidity of benzoic acids and basicity of anilines has been organized in grids to demonstrate the inductive and resonance effects. The relation between structure and pKa is emphasized by a new educational process: the Search-Organize-Predict (SOP) procedure.

Resumen El efecto de los sustituyentes en la acidez de ácidos benzoicos y la basicidad de anilinas ha sido organizado en cuadrículas para demostrar los efectos inductivos y de resonancia. Se hace énfasis en la relación entre la estructura y la pKa mediante un proceso didáctico nuevo: el procedimiento Buscar-Organizar-Predecir.

Abstract Based on IUPAC recommendations for the definition of the hydrogen bond, a series of grids is presented to provide instructors of introductory chemistry courses with visual examples of H-bridged systems. The grids show the interactions among various groups and sort the interactions into types, based on their significance in general chemistry. Examples are organized by second-row elements, third-row elements, anions and cations.

Resumen Basados en las recomendaciones de la IUPAC para la definición del enlace de hidrógeno, presentamos una serie de cuadrículas para proveer a los docentes instructores de cursos de Química General con ejemplos visuales de sistemas de puentes de Hidrógeno. Las cuadrículas muestran las interacciones entre varios grupos y ordena las interacciones en tipos, basados en su importancia para la química general. Los ejemplos se encuentran organizados por: elementos de la segunda fila, elementos de la tercera fila, aniones y cationes.

Abstract The effect of substituents on the reactivity in electrophilic aromatic substitution has been organized in a grid to demonstrate the inductive and resonance effects. This scheme can also incorporate the competition between donation and withdrawal of electron density. In class games are proposed from which undergraduate students can practice the effects while playing.

Resumen El efecto de los sustituyentes en la reactividad de la sustitución electrofílica aromática ha sido organizado en cuadrículas para demostrar los efectos de inducción y resonancia. Este esquema podría incorporar la competencia entre donación y extracción de la densidad electronica. Proponemos actividades en clase, en las cuales los estudiantes pueden practicar los efectos mientras están jugando.

The importance of hybrid atomic orbitals, both historically and mathematically, is reviewed. Our new analysis of the original derivation of the sp3, sp2, sp model reveals serious errors. Based on a critical survey of the literature, we submit six formal criteria that deprecate the use of hybrid orbitals in a pedagogical context. A sound mathematical basis of sp3 and sp2 formulae does not exist; hybrid atomic orbitals have hence no legitimate role in the teaching of organic chemistry.

The importance of hybrid atomic orbitals, in both general and organic chemistry, is reviewed. Every contemporary textbook of organic chemistry introduces the directed-valence (e.g. sp3, sp2, sp) model, but the suitability of these hybrid orbitals for use in the teaching of molecular structure has been increasingly questioned. Based on a critical survey of the literature, we submit seven practical criteria that deprecate the use of hybrid orbitals in a pedagogical context. We suggest how the teaching of organic chemistry without hybrid orbitals will provide students with an enhanced education.